The Mosquito Research and Control Unit (MRCU) announced on Thursday 7 July that the pperational roll-out of a technique involving genetically modified Aedes aegypti mosquitoes to combat the Zika virus will come a week after the first confirmed cases of Zika in the Cayman Islands.
On Tuesday 5 July, Acting Medical Officer of Health Dr Samuel Williams-Rodriguez confirmed the first two Cayman Islands cases of the virus, imported by returning residents who contracted the virus overseas. The two patients, both female, showed a travel history to locations where it is suspected the virus was contracted.
One travelled to a country where there is an outbreak of Zika last month and reported onset of symptoms to the HSA on 25 June. The second recently completed high school in a country where there is a Zika outbreak. After she returned home on 19 June she also sought medical treatment on 25 June after two days of symptoms.
Dr Williams-Rodriguez said there is still no evidence of local transmission of Zika in the Cayman Islands. However, as a proactive measure intended to get ahead of any potential outbreak in the Cayman Islands, the Mosquito Research and Control Unit (MRCU), in collaboration with biotechnology company Oxitec, is releasing the mosquitoes as a preventative measure to control the mosquito responsible for the transmission of Zika and other viruses.
The technique uses genetically engineered, non-biting sterile males to mate with local female Aedes aegypti mosquitoes, which then have offspring that die before reaching adulthood. Operations are scheduled to begin on Thursday, 14 July or soon after that, depending on the weather and other environmental conditions.
According to a press release from MRCU, the treatment area in West Bay comprises 300 acres between Watercourse Road, Powell Smith Lane, Rev Blackman Road and Hell Road. In the region of 100 to 200 pots, each containing approximately a thousand male mosquitoes, will be released three times a week.
“With our first confirmed cases of Zika, which were both imported, it is more important than ever that we get this additional control in place to help prevent any local transmission of mosquito-borne viruses,” said MRCU Director, Dr Bill Petrie. “We cannot stop mosquito-borne viruses from reaching our shores, but this technique will allow us to reduce the population of Aedes aegypti to help effectively prevent transmission.”
The emergence of Zika virus in the Americas has coincided with increased reports of babies born with Microcephaly, which is defined as abnormal smallness of the head, a congenital condition associated with incomplete brain development.
On Feb 1, 2016, the World Health Organization (WHO) declared the suspected link between Zika virus and microcephaly to be a Public Health Emergency of International concern and are presently seeking to re-define Zika as a Congenital Syndrome that represents a clear and present danger across the globe.
Shedding new light on the effects of maternal Zika carriage for the developing fetus, a pair of Lancet studies, published on 29 June suggest that Zika may cause other congenital defects that may not become apparent until the child is much older.
According to the study published, the Zika virus epidemic that started in Brazil has led to thousands of cases of devastating neuropathology and miscarriage, stillbirth, and neonatal death. The US Centers for Disease Control and Prevention has concluded that Zika virus causes microcephaly and other fetal brain defects.
Public fears have spread across the region and the continental United States concerning Zika against the backdrop of the effects of the virus on pregnant women who pass on the virus to their babies, who are often born with abnormal head circumference, and reports continue to suggest these effects could still cause neurological damage at birth as well as the child develops. WHO has confirmed the virus is also linked to other serious medical conditions such as Guillain-Barre Syndrome, which can lead to total paralysis.
Earlier this year, WHO recommended pilot deployment of the Oxitec technique, under operational conditions, to respond to the Zika crisis, declared in February to be an international public health emergency.
In the Cayman Islands, the project was reviewed by the Department of Agriculture, the Department of Environment, the National Conservation Council, and official approval granted. As well as in Grand Cayman, Oxitec is now currently deploying the technique operationally in Brazil in an area of 60,000 people, where residents have been severely affected by the Zika virus.
Known as the “Friendly Aedes aegypti Project”, the safety and efficiency of the technique was demonstrated through field releases in East End in 2009 and 2010, as well as Brazil and Panama. The Aedes aegypti population was reduced by more than 90 per cent in the areas where these releases took place.
“I remind the public that this technique has been through all the evaluation and approval stages relevant to the Cayman Islands,” said Dr Petrie. “This is an operational roll-out at a time when we are facing a public health imperative.”
In Grand Cayman, the Oxitec technique will be integrated with traditional controls using insecticides, which are increasingly less effective.
The treatment phase in West Bay is expected to last around nine months and then be rolled out across Grand Cayman, subject to the relevant approvals. Cayman Brac and Little Cayman are not affected by the Aedes aegypti mosquito.